Conventionally, headphones with a noise-canceling function to cancel external noise are known. Japanese Unexamined Patent Publication No. 2012-023637 discloses a technique that attenuates noise by driving a driver unit with a noise-canceling signal which cancels noise from outside collected by a microphone in a front air chamber provided between a housing of a headphone and an ear of a user.
Although a headphone that cancels external noise with a feedback system attenuates external noise, not all noise is eliminated due to a variety of causes like sound reflection inside an ear cup and characteristics of a microphone and a driver unit. Furthermore, the noise-canceling signal may include components that cannot cancel the external noise since the noise-canceling sound emitted from the driver unit is collected by the microphone. As a result, the noise-eliminating effect of the noise-canceling function was diminished. Improvement of the noise-eliminating effect of the noise-canceling function is desired.